Snap-action current interruption diaphragm system for over-pressurized electrochemical cells

Abstract

An active metal non-aqueous electrochemical cell including a lithium anode, an organic electrolyte system, a cathode contained in a cell housing, and at least one hermetically sealed pin-type lead extending through a cell header is provided with an hermetically sealed, pressure and/or temperature actuated, snap-action header diaphragm disconnect mechanism fixed to, and which snaps outward to disconnect, the pin terminal from the internal cell lead in response to elevated internal pressure reaching a sufficient amount to operate the snap-action mechanism. The position of the snap-action header diaphragm is visible outside of the cell.

What is claimed is: 
     
       1. In an active metal, non-aqueous electrochemical cell having electrodes including a lithium anode, an organic electrolyte system and a cathode contained in a cell housing, at least one compression or hermetically sealed pin terminal connected to a cell electrode lead and extending through a cell header, the improvement comprising: an hermetically sealed, pressure actuated, snap-action header diaphragm disconnect mechanism fixed to the pin terminal, and which snaps outward to disconnect, the pin terminal from the cell electrode to which it is connected in response to the internal pressure reaching a predetermined amount to operate the snap-action mechanism and wherein the position of the snap-action header diaphragm is visible from outside of the cell.   
     
     
       2. The apparatus of claim 1 wherein the pin terminal is reconnectable upon sufficient reduction of internal cell pressure and wherein the header diaphragm snaps back to its original position when the internal pressure is sufficiently reduced. 
     
     
       3. The apparatus of claim 1 wherein the elastic limit of the header diaphragm is exceeded by the predetermined amount of pressure causing a permanent outward deformation of the header membrane, thereby permanently disconnecting the lead. 
     
     
       4. The apparatus of claim 1 wherein the snap-action mechanism operates to sever the pin of the pin terminal lead connection permanently. 
     
     
       5. The apparatus of claim 1 wherein the electrolyte is ester-based. 
     
     
       6. An active metal, non-aqueous bipolar electrochemical cell having electrodes including a lithium anode, and a cathode, and an organic electrolyte system, contained in a cell housing, an hermetically sealed pin terminal lead connected to the anode or the cathode and extending through a cell header, an hermetically sealed, pressure actuated, snap-action header diaphragm disconnect mechanism fixed to, and disposed to snap outward to disconnect, the pin terminal from the electrode to which it is connected in response to elevated internal pressure reaching a sufficient amount to operate the snap-action mechanism, the position of the snap-action header diaphragm being visible from outside of the cell. 
     
     
       7. The electrochemical cell of claim 6 wherein the snap-action is irreversible. 
     
     
       8. The electrochemical cell of claim 7 wherein the snap-action reversibly reconnects the pin terminal and restores operable integrity to the cell. 
     
     
       9. The electrochemical cell of claim 6 wherein the snap-action permanently severs the pin terminal lead. 
     
     
       10. An active metal, non-aqueous bipolar electrochemical cell having a pair of electrodes including a lithium anode and a cathode, and an organic electrolyte system contained in a cell housing, an hermetically sealed pin terminal lead connected to the anode or the cathode and extending through a cell header, an hermetically sealed, pressure actuated, bimetallic snap-action header diaphragm disconnect mechanism fixed to, and disposed to snap outward to disconnect, the pin-type lead from the connected internal cell lead in response to elevated internal pressure reaching a sufficient amount to operate the snap-action mechanism, the position of the snap-action header diaphragm being visible outside of the cell. 
     
     
       11. The electrochemical cell of claim 10 wherein the snap-action is irreversible. 
     
     
       12. The electrochemical cell of claim 10 wherein the snap-action reversibly reconnects the pin terminal and restores operable integrity to the cell. 
     
     
       13. The electrochemical cell of claim 10 wherein the snap-action permanently severs the pin terminal lead.